Missouri-Johnson, 1987), and invarious natural history studies conducted on snakes instates adjacent to or near. Arkansas (e.g., see studies byKlimsta inIllinois ...
i
Vertebrate Prey of Selected Arkansas Snakes Stanley E. Trauth Department of Biological Sciences Arkansas State University State University, AR 72467-0599
Chris T.McAllister Department of Biology Texas Wesleyan University 1201 Wesleyan Fort Worth, TX76105-1536
Introduction
Material and Methods
Allsnakes are carnivorous and often represent the dominant predatory species in food chains of terrestrial ind aquatic communities. Snake food habits, feeding behavior, and tropic ecology have been extensively documented (Mushinsky, 1987). Food lists on the dietary preferences of North American snakes can be found in virtually any study on snake ecology. Snakes often eat a variety of vertebrate prey (often including snakes themselves [e.g., see appendix in Greene, 1988]); vertebrates constitute the principal component of the diet in 95 of 116 snakes species (82%) reported by Mushinsky (1987). Only recently has the snake diet literature begun to emphasize foraging theory and the interrelationships between predator and prey (see review by Arnold, 1993). Research on vertebrate prey of Arkansas snakes in limited to mostly anecdotal accounts (e.g., Trauth, 1982; Byrd et al., 1988; Trauth and Cochran, 1991) compared to the food habits information amassed for snakes typically inhabiting the southcentral United States. These diet data are summarized or referenced in the snake life histories of Wright and Wright (1957) or inrecent herpetological textbooks (e.g., Ernst and Barbour, 1989; Ernst, 1992), in annotated state bibliographies (Texas-Dixon, 1987; Oklahoma-Carpenter and Krupa, 1989), in state herpetological books (Louisiana-Dundee and Rossman, 1989; Missouri-Johnson, 1987), and in various natural history studies conducted on snakes in states adjacent to or near Arkansas (e.g., see studies by Klimsta in Illinois and by in Kansas as cited in Smith [1961] and Collins 1993], respectively). In the present study, we documented vertebrate prey of several Arkansas snake species through the dissection of museum specimens. Our primary objective was to genrate new information on the food habits of several snake pecies found within the state. A dietary study such as ours contributes to an understanding of the following: 1) snake's habitat choice, 2) variation in annual and seaonal food consumption, 3) ontogenetic dietary shifts, 4) ompetition for available food resources, and 5) geojraphic differences in selected food. Finally, our food labits study represents a preliminary list for these snakes n Arkansas and adds to a database of knowledge on their ife history.
We analyzed the stomach contents of 14 species and subspecies of snakes collected in Arkansas and housed in the Arkansas State University (ASU) herpetological collection. A total of 510 specimens, most of which were collected over a 10-year span (1984-1993), was examined. The alimentary tract of each specimen was entered via a midventral incision; many of these animals had previously been necropsied to determine their reproductive condition (Trauth et al., 1994). Snout-vent length (SVL) and sex were recorded for all dissected snakes (as well as for some of the prey species). Allprey items (including, in some cases, invertebrates) were placed in plastic bags or glass jars filled with 70% ethanol, retained as voucher specimens, and deposited in the ASU herpetological collection. For convenience, each species was grouped according to adult body size, mode of reproduction, and familial rank (see Trauth et al., 1994). A majority of the snake specimens utilized to compile Table 1 was collected during spring months (March May). Common and scientific names of snakes followed Conant and Collins (1991).
{'itch
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Results and Discussion
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Small Oviparous Colubrid Species. The northern scarlet snake, Cemophora coccinea copei, is well known for its egg-eating habits (see Mushinsky, 1987; Trauth, 1993). Of the 18 specimens examined, we found lizard eggs (and/or eggshells) in three individuals (17%). One specimen had consumed six eggs, whereas the other two contained three and five eggs. Inall cases, the eggs appeared to be those of the six-lined racerunner (Cnemidophorus sexlineatus).
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Medium-sized Oviparous Colubrid Species. Ernst and Barbour (1989) summarized the literature on food habits of the eastern hognose snake (Heterodon platirhinos). Although toads of the genus Bufo are favorite prey in this species, we found toads in only four of 78 animals (5%). Trauth (1982) reported the consumption of spotted salamanders (Ambystoma maculatum) from a snake collected near YellvilleinMarion County. The diet of the red milk snake (Lampropeltis triangulum syspila) was reviewed by Williams (1988). We found
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Vertebrate Prey of Selected Arkansas Snakes
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Table 1. Vertebrate prey items from the stomachs of 10 species of snakes collected in Arkansas. Abbreviations for snake species are followed by the total number ofstomachs examined (inparentheses). Thamnophis p. proximus TPP (77); Masticophis f.flagellum MFF (36); Lampropeltis getula holbrooki LGH (84); L. c. calligaster LCC (28); L.triangulum syspila LTS (39); Elaphe o. obsoleta EOO (66); Coluber constrictor priapus CCP (46); Agkistrodon c. contortrix ACC (87); A.piscivorus leucostoma APL(66); Sistrurus miliarius streckeri SMS (19). Snake species listed in this table have more than one type of prey item; see text for additional details and remarks.
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CCP
EOO
LTS
LCC
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LGH
MFF
TPP
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SMS
ACC
APL
Class Osteichthycs Order Perciformes Family Centrarchidae Lepomis cyantllus
X
Unidentifiable sunfish
X
Class Amphibia Order Caudata Family Ambystomatidae Ambystoma maculatum larva Family Plethodontidae Desmognathus brimUyorum Order Anura Family Bufonidae Bufo sp.
X X
X
Family Hylidae Acris crepitans blanchardi
X X X
Hyla cintrea Hyla versicolor/chrysoscelis Unidentifiable hylid sp. Family Ranidae Rana utricularia
X
X X
X
Family Microhylidae
Gastrophryne carolinensis Class Reptilia Order Sauna Family Phrynosomatidae Sceloporus undulatus hyacinthinus Family Scincidae Eumeces fasciatus Eutneces laticeps ScinctUa lateralis
X
X
X
XX X X
Unidentifiable Eumeces Family Teiidae Cnemidophorus sexlineatus viridis C. s. viridis eggs Order Serpentes Family Colubridae Coluber constrictor priapus
X
X
XX
X
X X X X
X X
X
X
X
Microtus pinetorum
Mus musculus Neotoma floridana Ochrotomys nuttulli
Sigmodon hispidus Unidentifiable rodent Order Lagomorpha Family Leporidae SylviUtgus floridanus Order Insectivora Family Soricidae Cryptotis parva
X X
X
Unidentifiable colubrid snake Snake eggs
Orywmys palustris Peromyscus leucopus Pemmyscus maniculatus
X
X
Thamnophis s. sirtalis
Class Aves Order Passeriformes Family Icteridae Agelaius phoeniceus Class Mammalia Order Rodentia Family Muridae Microtus ochrogaster
X
XX
X
Diadophis punctatus
Nervdia rhombifer Nerodia erythrogasterflairigaster Opheodrys aestivus Storeria occipitomaculata
X
X XX
XX X
X X
X
X
X X
X X
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X X
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:>nly lizards species (Table 1) in three specimens (8%). One of the prey items (C. sexlineatus) was not mentioned n the listing of natural foods by Williams (1988), llthough this species was reported by Knight and Collins (1977) in a milk snake from Kansas. Large Oviparous Colubrid Species. Clark (1949) and Fitch (1963a) provided the most detailed studies on food habits of the black rat snake (Elaphe obsoleta obsoleta); the investigations were conducted in Louisiana and Kansas, respectively. Both studies found mammals and birds to be the most abundant prey. We found voles, mice, rabbits, and red-winged blackbirds in 6% of our sample of mostly adult snakes. The speckled kingsnake (Lampropeltis getula holbrooki) consumes a variety of vertebrates but usually prefers reptiles and especially reptilian eggs. A summary of prey species is shown in Table 1. We found three specimens (850, 1205, and 829 mm in SVL, respectively) whose stomachs contained 1, 2, and 10 snake eggs. One immature adult female (705 mm in SVL) collected in Clark County had eaten a Quachita dusky salamander; this may represent the first record for this prey item in the speckled kingsnake. A speckled kingsnake was observed eating a hognose snake (H. platirhinos) in Searcy County (G. L. Harp, pers. comm.); copperheads (Agkistrodon contortrix) have been taken by captive snakes. Thirteen percent of our sample contained vertebrate prey. The food preferences of the prairie kingsnake (L. c. calligaster) have been reviewed by Ernst and Barbour (1989); mammals represent the most common prey. Only mammals (shrews, voles, and juvenile woodrats) were bund inthe stomachs of five specimens (18%). One of us SET) observed predation on C. sexlineatus by a juvenile jrairie kingsnake in eastern Oklahoma (Trauth, 1983). The southern black racer (Coluber constrictor priapus) s an opportunistic feeder, preying on a diversity of vertebrates as well as invertebrates. Among the most common vertebrate prey in our specimens were lizards (skinks) and nakes. Skinks were found in 24% of stomachs examined. However, invertebrates (crickets and grasshoppers) were also found in 24% of specimens. Fitch (1963b) summarized food for all subspecies of C. constrictor throughout ts range in North America. Our study revealed similar >rey items compared to other subspecies reported from different geographic regions. Although Mushinsky (1987) made no reference to the bod habits of the eastern coachwhip (Masticophis flagelum flagellum), Carpenter (1958) briefly reported on this species from Oklahoma. He found lizards and birds in the diet. Lizards were the primary prey, being found in all pecimens containing food remains (33%). Cnemidophorus exlineatus was the most common prey species. We have observed coachships on several occasions hunting for colared lizards (Crotaphytus collaris) in rock quarries and on
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vj*ixa
*..
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cedar glades inArkansas. Medium-sized Viviparous Colubrid Species. Amphibians represented the only food group recorded for two species of Thamnophis in our study. Prey of the eastern garter snake (Thamnophis sirtalis sirtalis) consisted only of toads (Bufo sp.) in the present study. Predation by this species on wood frogs (Rana sylvatica) was mentioned by Trauth et al. (1995). The western ribbon snake (T. p. proximus) consumed salamander larvae and anurans (Table 1). Only eight stomachs (10%) contained food remains. Ernst and Barbour (1989) surveyed the diet literature on these two species. Clark (1974) found that amphibians represented 92% of the diet in T. p. proximus. Small Viperid Species. The diet of the western pigmy rattlesnake (Sistrurus miliarius streckeri) consisted of reptiles (lizards and snakes). Food items were found in 4 of 19 stomachs (21%) examined in this study (Table 1). Trauth and Cochran (1991) reported a predatory interaction between this species and a four-toed salamander (Hemidactylium scutatum) inGarland County. Medium-sized Viperid Species. A variety of small rodents (Table 1) represented the only prey group found for the southern copperhead (Agkistrodon contortrix contortrix). Nine percent of the stomachs contained food items. Woodland voles (Microtus pinetorum) were the most common mammal. Fitch (1960) provided a detailed summary on the food habits of copperheads. We found fish, anurans, small mammals, and snakes as food items (Table 1) for the western cottonmouth (A. piscivorus leucostoma). In one instance, a cottonmouth (651 mm in SVL) was collected along a rice field near Newport, Jackson County, in the process of consuming a previously-killed and decapitated yellowbelly watersnake (770 mm inSVL). This type of scavenging has been previously reported in this species (Berna and Gibbons, 1991). Fifteen percent of the stomachs we examined contained prey items. Burkett (1966) provided a detailed listing of vertebrate prey in this species from studies conducted in states surrounding Arkansas. Large Viperid Species. Ernst (1992) furnished a comprehensive list of prey for the timber rattlesnake (Crolalus horridus). We examined eight specimens; one stomach contained two young gray squirrels (Sciurus caro-
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linensis).
In summary, vertebrate food items of 14 species and subspecies of snakes were examined. The snake samples included medium-sized to large forms (both terrestrial and aquatic, but excluded Nerodia species). The samples comprised 10 genera (Agkistrodon, Cemophora, Crotalus, Coluber, Elaphe, Heterodon, Lampropeltis, Masticophis, Sistrurus and Thamnophis) in two families (Viperidae and Colubridae). We found 34 different species of vertebrate prey. Anurans were the dominant prey of two species of Thamnophis and in H. platirhinos. Lizards were the domi-
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Vertebrate Prey of Selected Arkansas Snakes
food items in M. flagellum, L. triangulum syspila, Coluber (C. constrictor priapus), and S. miliarius streckeri. The ground skink (Scincella lateralis) was the most utilized reptilian prey item. Snakes predominated in the diets of Lampropeltis (L. getula holbrooki) and A. piscivorus leucostoma, but were also found inM.flagellum and C. constrictor priapus. Mammals were obtained mostly inL. c. calligaster, E. o. obsoleta and A. contortrix; voles led as the dietary preference of these snakes. Reptilian eggs were found in the stomachs of Cemophora (C. coccinea), L. g. holbrooki and M. flagellum. The food habits data presented herein represent a preliminary listing for these snakes; future studies would benefit by incorporating more snake species and by addressing invertebrate prey as well. Studies of ecoregional variation in dietary habits of snakes within Arkansas are currently being undertaken. Acknowledgments. We thank the many students and colleagues who provided field assistance from 198494. Collection of snakes was under the authorization of the Arkansas Game and Fish Commission through scientificcollection permits issued to SET. nant
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